I don't see each machine as replacing a checkout. Checkouts aren't utilised efficiently. You'll never see enough open to cope with the customers...even for the times there's a steady flow. And someone has to oversee the machines for hiccups and customer theft. These machines relieve the pressure on the mimimal existing checkouts...end result is you get served faster whilst I check myself out.
Likewise...school kids get the shifts because others won't do it.
